McMaster University | Department of Chemistry

Structuring Silicone Elastomers
Vinodh Rajendra

While silicone elastomers possess many interesting properties for use as biomaterials, their hydrophobicity, particularly when the objective to delivery polar drugs, including proteins, is problematic: it is challenging to disperse the polar drug into the elastomer, and subsequent controlled release is also problematic. Our objective was to develop strategies that would permit the controlled synthesis of hydrophilic structures within a silicone elastomer, with the idea that this hydrophilic control could be linked to desired delivery protocols. As artifacts, silica microspheres were found within these elastomers and were investigated on the different conditions in which they can form. Formation of silica microspheres within silicone oil is unheard of and as a result a novel method in forming them.

Through Room Temperature Vulcanization (RTV) of silicones, investigations on asymmetric cure, surface roughness, and internal hydrophilic structuring were done as a function of the synthetic formulations. By varying simple parameters such as the weight% of crosslinker, catalyst, surfactant and relative humidity, we were able to control the homogeneity of our elastomers, achieve surface roughness values (Rq) ranging from 400nm - 65µm, and create internal hydrophilic structures ranging from dispersed globules to interconnected channels. The formation of silica microspheres was also tested by varying similar parameters including using different types of amine-based catalysts. This resulted in the formation of different types of silica structures and in their distribution.